Fuel reformers, or fuel processors, are capable of converting a hydrocarbon fuel such as methane, propane, natural gas, gasoline, diesel, and the like, into various lower molecular weight reformates such as hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), nitrogen (N2), and water (H2O). Reformers can be produced in various configurations, such as, steam reformers, dry reformers, or partial oxidation reformers.
Steam reformers react fuel and steam (H2O) in heated cylinders filled with catalytic media. Generally endothermic, heat is transferred into the cylinders, which promotes the conversion of hydrocarbons into primarily hydrogen and carbon monoxide. An example of the steam reforming reaction is as follows:CH4+H2O→CO+3H2
Dry reformers produce hydrogen and carbon monoxide in the absence of water, employing oxidants, such as carbon dioxide, in the presence of catalysts. Similar to steam reformers, dry reformers are also endothermic and adsorb heat in order to encourage conversion. An example of a dry reforming reaction is depicted in the following reaction:CH4+CO2→2CO+2H2
Partial oxidation reformers burn a fuel/oxidant mixture in the presence of catalysts to convert the reactants into reformate, such as, carbon monoxide and hydrogen. Partial oxidation reformers generally comprise a mixing zone 26 and a reforming zone to provide this function. In the mixing zone 26, the oxidant and a fuel are mixed to form a fuel mixture. In the reforming zone, the fuel mixture undergoes an exothermic reaction, generally within a catalytic substrate, which comprises catalysts capable of converting the reactants into the desired reformate. The process is exothermic and temperatures of about 600° C. to about 1,600° C. (degrees Celsius) can be experienced. An example of the partial oxidation reforming reaction is as follows:
            CH      4        +                  1        2            ⁢              O        2              →      CO    +          2      ⁢              H        2            
Reformers may be used in multiple applications. One such application is an emissions abatement system for stoichiometic or lean-burn gasoline and diesel-powered vehicles, which can employ a partial oxidation reformer to convert liquid on board fuel (e.g., gasoline, diesel fuel, biodiesel, alcohol, oxygenated fuels) into reformate. Reformate can generally comprise hydrogen and carbon monoxide, which can be used to fuel the engine to produce low emissions, and/or fed to the exhaust aftertreatment system to enhance its performance. However, during start-up of the reformer when the catalytic substrate is below its normal light-off temperature, reformate is not produced, which results in higher emission production and/or less efficient exhaust aftertreatment.
Consequently, there is a need to further reduce start-up times and hopefully to reduce or eliminate the amount of undesirable emissions produced during reformer start-up. This is especially of concern as the emission requirements for passenger and freight vehicles are becoming increasingly more stringent.